Methods of making structural materials having a low temperature coefficient of the modulus of elasticity



1970 s. STEINEMANN ETAL 3,547,713

METHODS OF MAKING STRUCTURAL MATERIALS HAVING A LOW TEMPERATURECOEFFICIENT 0F THE MODULUS OF ELASTICITY 1 3 Sheets-Sheet 1 Filed April1s. i967 Fig. 10

1y I fi Per/0o m VENTORS MAP/7N 1 672 1? A TTOR'N 5 Y5 SAMOHSITM/[MA/V/V A/V/l 1970 s. STEINEMANN ETAL 3,547,713

METHODS OF MAKING STRUCTURAL MATERIALS HAVING A LOW TEMPERATURECOEFFICIENT OF THE MODULUS OF ELASTICITY Filed April 18. L967 3Sheets-Sheet 6 Fig. 4

Elements:

Group 118 I115 IVB vs VIB VIIB ,vnl

Period 1v Ca Sc Ti v Cr Mn V Sr y Zr Nb Mo Tc Ru' Rh Pd VI Bu Lo Hf Tu WRe Os Ir Pt lanrhanons ad'inides I Q E] cubic {-aLe cenlcrcd Structuresof crystal and approximate pogih'an of H1: {5 cubic cenl-c edphase'limiks inrhc alloqs hflqsoniu l r K complex high mmm O E] W W Hroom l' mfemhu O O E] El 0 O E] E] SAMUEL STE/NfMA/V/V AND MART/N PETE/ZMWMMM H TTORNEIS United States Patent O 3,547,713 METHODS OF MAKINGSTRUCTURAL MATE- RIALS HAVING A LOW TEMPERATURE COEF- FICIENT OF THEMODULUS F ELASTICITY Samuel Steinemann, Waldenhurg, and Martin Peter,Petit- Lancy, Switzerland, assignors to Institut Dr. lug. ReinhardStraumann A.G., Waldenburg, Switzerland, :1 jointstock company ofSwitzerland Filed Apr. 18, 1967, Ser. No. 631,686 Claims priority,application Switzerland, Apr. 22, 1966, 5,878/66 Int. Cl. (122E 1/00 US.Cl. 148-115 20 Claims ABSTRACT OF THE DISCLOSURE Method of producing ametallic, paramagnetic crystallized structural material of a temperaturecoetficient of the modulus of elasticity between per degree and +10 perdegree centigrade. The components of the material are selected in typeand quantity such that the material exhibits an atomic, paramagneticsusceptibility x 50-10- emE/g.-atom at room temperature and a negativetemperature coefficient of the susceptibility d /a'T. The components aremelted together, and a preferred orientation of the crystals by at leasta mechanical or a thermal treatment of the material is produced.

The present invention relates to methods of making structural materialsand elements having a low temperature coeflicient of the modulus ofelasticity and more particularly having such coeflicient varying onlyslightly around zero.

In mechanical oscillatory systems, such as clocks and electromechanicalfilters, but also in spring systems such as balances, levellingapparatus, electric measuring devices and so on, structural elements,e.g. elastic bodies are employed, whose modulus of elasticity isrequired to be independent of temperature as far as possible. Cases canhowever occur wherein the elastic body should have a temperaturecoefficient of the E-modulus which is somewhat ditferent from Zero inorder that all temperaturedependent influences of an oscillatory systemshall be compensated simultaneously, an example being the increase inthe moment of inertia caused by the thermal expansion of a balancewheel. Moreover this compensation, under various stress conditions,affects quite different moduli, namely the modulus of elasticity (forexample in the bending of tuning forks, spiral springs etc), the shearmodulus (under torsion, for example, in spirally wound tension springs)or the compression modulus, as well as combinations of all of thesemoduli.

The known structural materials which exhibit suitably small andadaptable temperature coefficients are based upon ferromagneticprocesses. In these materials under the influence of external load,there is a change in the local direction of the spontaneousmagnetization in such a manner that the magnetostrictive distortioncaused by the change in magnetization increases the shape changingeffect of the load on the body (this is known as magnetostrictiveextension under tension and conversely, according to the direction ofstress). Thus, in a ferromagnetic body, in addition to the purelyelastic extension as the result of a stress there is to be added also amagnetostrictive extension, and as contrasted with the perfectly elasticHooke relationship the elasticity modulus therefore decreases. Thiselevation is known as the AE effect. The A E effect is particularlystrong in the pure metals Ni, Co, Fe and is brought about essentially bythe linear magnetostriction effect and is practically suppressed byexternal magnetic fields or cold working (both of which disturb the freeinception of the spontaneous magnetization in the domains). If, on theother hand, the volume magnetostriction effect is preponderant, as forexample for certain Fe-Ni, Fe-Ni-Co and Fe-Co-Cr alloys and others, thenthe anomalous behaviour in the ferromagnetic temperature region does notcompletely vanish even under conditions of magnetic saturation orintense cold working. As the magnetostriction like the spontaneousmagnetization falls ofl with increasing temperature, these effects canproduce the known behaviour of the E modulus if there is suitable choiceof the alloy, so that in many alloys the volume effect is made use of.These theories are described in the text books by R. Becker and W.Doring: Ferromagnetismus, Springer Verlag, Berlin, (1939), pp. 336-357;R. M. Bozorth: Ferromagnetism, D. Van Nostrand Company, New York,(1951), pp. 684-699.

Nevertheless the elastic behaviour of these alloys does always exhibit amore or less strong dependence upon magnetic field. For example, thevibration frequency of a tuning fork changes directly in a magneticfield as does also its temperature coeflicient. On the other hand, thetechnological processes necessary for the precise adjustment of atemperature compensation are quite diflicult. An accurate cold workingand heat treatment is necessary in order to make the compensation rangeas large as possible and to obtain small temperature coeflicients. Thesecold working treatments and final heat treatments in fact change theinner microscopic and sub-microscopic state of stress in the metal (onaccount of dislocations, precipitations, etc., but the chemical changeof the phase composition involved by the precipitation hardening is notsubstantial) and thus have a sensitive influence upon the temperaturebehaviour and the elasticity modulus. On the other hand, especially whenthe anomalous behaviour is based upon a predominating volumemagnetostriction etfect, the texture influence is less apparent.

The present invention relates to a method of producing structuralmaterials, of the elinvar type having a small temperature coefficient ofthe elastic moduli, which are sensibly temperature independent. Themethod uses a paramagnetic material with an atomic susceptibility x50-10 emE/g.-atom at room temperature and a negativetemperature-coeflicient of this susceptibility, e.g. d /dT, and whereina texture is produced by mechanical or heat processing. This texture isrelated to the type and orientation of the stress in the structuralelement.

It is advantageous that the overall composition, or that of principalphase of the material, has an electron concentration e/ a comprised ine/ a equal to 2.5-3.7 or 4.1-5.7 or 6.1-7.8 or

The electron concentration e/a is the ratio of the mean number ofelectrons situated externally of closed shells, that is to say theelectrons determining bonding, to the number of atoms. Thus in an alloyconsisting of n elements with the percentages by weight g,, the atomicweights A, and the number 1/, of electrons outside the closed shells(valencies) the atomic percentages are calculated by and the electronconcentrations are given by e 1 11 run The product-sum 1 is given by theexpression i =1 m +l n +m n in the case of cubic materials and is givenby for hexagonal materials wherein l, m and n are respectively thedirection-cosine of the measurement or stress direction with respect tothe main axes of the cubic crystallite, and, in the case of hexagonalmaterials, 0, is the direction-cosine of the measurement or stressdirection with respect to the hexagonal axis.

The mechanical or heat processing used to produce the texture may bedrawing, or rolling or recrystallization annealing. The texture ischaracterised by the product-sum I of the direction-cosine between thecrystal-orientation and the stress direction in the structural element,taken as the mean over all crystallite orientations in the material. Theproduct-sum i is given by the expression in the case of cubic materials.Advantageously, for cubic materials I 0.2 for the elasticity modulus,and I 0.2 for the shear modulus (stress axis=torsion axis). In the caseof hexagonal materials I O.25 for the elasticity modulus and I O.25 forthe shear modulus.

For an understanding of the invention relative to the above mentionedmaterials, which are essentially different from materials previouslyproposed for the problem, the characteristic principles of thesematerials will now be explained.

The cohesion energy of a metal is comprised additively of variouscontributions. Essentially there are three components of the energy tobe considered, which originate from the interaction between the ions ofthe crystal lattice, between the ions and free electrons and between thefree or itinerant electrons themselves. The first two components areresponsible for definite uniform characteristics of the elasticbehaviour of the single crystal; on the other hand the last component isdecisive for certain metals and alloys, in particular in respect of thetemperature relationship of the elasticity (usually this component dueto the electron gas is small or independent of temperature). Upon theseeffects depends a group of materials of this invention, principallymetals and alloys but under certain circumstances also semiconductors.These materials are not ferromagnetic and satisfy also the furtherrequirements of resistance against corrosion, easy workability, smallmechanical losses, mechanical strength and so on.

If the electrons make a decisive contribution to the cohesioncharacteristics, then their energy as a whole must be large, for whichthe effective density of states at the Fermi level N(E is determinative.If, in fact, under such conditions the crystal lattice is elasticallydistorted by mechanical stress, then this results also in a distortionof the Brillouin body and the kinetic energy of the free electronsexercises marked influence upon the elastic behaviour of the crystal.The mechanism is naturally effective with any stress upon the solidbody; thus in the case of a dilatation for the compression modulus K(electrons in the nearly empty band and holes in the nearly filled bandact in an equivalent manner), and in the case of pure shear (withoutdilation) and a corresponding distion of the Brillouin body, there willtake place an increase of the kinetic energy in some directions and areduction of these energies in other directions, which then results inan electron transfer (figuratively electron evaporation); this has beentheoretically investigated in the special case of aluminimum by RS.Leigh (Philosophical Magazine, vol. 42, pages 139 et. seq. 1951).

If the electronic contribution to the elastic energy is high, then alsotemperature influences upon the kinetic energy of the electrons (orholes respectively) or indirectly upon fi(E which can be expressed asthe temperature coefiicient 011V E dT will predominate in the elasticbehavior of the crystal (the derivative 011V E1. d '1 is introduced in aformal manner). If the value of dN(EF) dT is negative, the temperaturecoefiicient of the elastic moduli becomes a positive contribution.

The high density of states fi(E is characterised by high paramagneticsusceptibility high specific heat of the electrons, and frequently alsoby a high superconductivity transition temperature. The temperaturerelationship with KLE is most clearly seen from the temperaturebehaviour of )4 namely d /dT.

The foregoing discussion has shown how itinerant electrons candecisively influence the elastic behavior. The relationships may be seenfrom FIGS. la-lc, in which there are represented, for the transitionelement of the third, fourth and fifth periods, and their alloys, theparamagnetic susceptibility (FIG. 1a), the temperature coefficientthereof ld dT (FIG. 1b) and the temperature coefficient of theelasticity modulus (FIG. 10), plotted in each case With respect to theelectron concentration e/a.

Materials which are applicable to the purpose of the invention come outwith a high value of X and a negative value of d /dT. The curves showalso that the applicable ranges of the electron concentration e/ a are:

2.53.7 4.1-5.7 6.1-7.8 and 9.3l0.5

The electron concentration e/a embraces completely all alloys with twoor more components between the elements of different groups and periodsof the period system.

With structural materials fulfilling the requirements of the invention,the contribution of the free electrons to the elastic energy results inan anomalous temperature relationship with the elasticity. These effectsare however contrasted with the conventional anomalous behaviour. Thetemperature independence of the previously known thermocompensatingalloys is always limited at an upper temperature, in fact at that pointwhere the required homomorphous transformations vanish; the reversibletransformation of ferromagnetism to paramagnetism is the most well-knownexample; this anomaly extends up to the Curie temperature.

In the drawings FIGS. 1a to 10 depict isotropic structures. FIGS. 2a to2] illustrates the dependence of orientation with temperature. FIG. 3depicts a pole figure for the cubic case. FIG. 4 illustrates the crystalstructures of the elements and the approximate phase structure of thebinary alloy series of the transition elements.

The FIGS. la to 10, in particular 10, refer to isotropic structures,e.g., all crystal orientations are equally prohable. The behaviour ofthese materials however is an anisotropic property of the crystal whichhas to be taken in account for the technical use in two ways; it caneither be provided a texture by suitable mechanical or heat processing,or the preferred orientation in the material as obtained with customaryprocessing is examined (for example with X-ray methods) and orientedagainst the stress direction in the structural element. Theseorientations are fully described by the product-sum 5. Structuralmaterials according to this invention should not only retain theirrigidity with varying temperature, its technical application needs alsosufficient mechanical strength which can be obtained through differentforms of hardening processes. In materials in accordance with thisinvention, such hardening processes are possible, but nevertheless, onaccount of the condition concerning the density of state orsusceptibility, the particular influence of the alloying elements, or ofthe other means for hardening, have to be taken into account. The highdensity of state of the itinerant electrons, as advanced in thisinvention, has furthermore the consequence that lattice faults (e.g.vacancies, dislocations, interstitial atoms, stacking faults, etc.), assuch are produced by quenching or cold-working, and impurities whichoccupy not the regular lattice places, but the so-called interstitialplaces (among these being for example gases and elements with small atomradii, as C, O, H, B, etc.) can behave in different manner than in anormal metal (as copper, aluminum, etc.). In what follows, these threegroups of phenomena will be examined in relation to the technicalrealisation of the invention.

Polycrystalline solid bodies may have, as is known, numerous anisotropiccharacteristics which originate from the texture (see the textbook by G.Wassermann and Johanna Grewen Texturen metallischer Werkstoffe, SpringerVerlag, Berlin, Gottingen, Heidelberg, 1962). It is however lessfrequently investigated how the temperature coefficients of theelasticity modulus can depend upon a texture. The AE effect of nickel,for example, is strongly anisotropic because the shape magnetostrictionis strongly anisotropic; in the classical alloys having a smalltemperature coeflicient of the E modulus, which are known under themarks Nivarox, Ni-Span C, etc., where the volume magnetostrictionpredominates, the direction dependence is, on the contrary, small and inpractice is not considered or controlled. On the other hand thematerials in accordance with the invention depend clearly upon singlecrystal properties, whose anisoptropic properties cannot be ignored orneglected.

The elasticity theory describes the strains in the me chanicallystressed single crystal by means of elastic constants. For the cubiccrystal, which in the following will be taken as an example, it willsuffice to consider three quantities, c and e (0 corresponds to extension along a main axis in which also the force is effective, C is anextension normal to this main axis and to the direction of the force,C44 is a shear in planes of two main axes). For the elastic energy andin particular the contribution of electrons, the following quantitiesare of importance:

wherein C and C correspond to two shears and K is the compressionmodulus. For the single crystal, there will then apply theconventionally used modulus E (elasticity modulus), G (shear modulus);see for example C. S. Barrett Structure of Metals, McGraw-Hill BookCompany, New York, 1952:

are the already mentioned direction-cosines between the stress axis andthe main axes of the crystal.

6 For the temperature coefficients of these moduli the following thenapply:

l 1. 5mi 19 2) 1%)] K dT 3K[ c dT c dT 1 01E 1 l 1 11C 1 *'EW lT W[(EWX5 J 1 1 d6 elon 1 dG l 1 d0 1 1 d0" -eEr- {e[(mr) n WWW} Thetemperature coefiicients of the conventionally used moduli K, G, Edepend on the temperature coefficients of the single crystal quantitiesC, C and K and the relative orientation of the stressing or measuringdirection (also for the direction of propagation of sound waves); forthe latter the values of some particular orientations in the cubiccrystal are I=:0 for l00 The special, fixed value of I /s is to beinserted in the above formula for the ideal isotropic polycrystallinematerial where general relations between the common moduli exist (seefor example W. Koester and H. Franz, Metallurgical Reviews, vol. 6, No.2, 1961):

These laws may be demonstrated, for example, for pure palladium, whichis one of the metals in the class of structural materials in accordancewith the invention. In FIG. 2 there are indicated the measured data for0:0 CIZIAZ (cu-C12), and therefore K, E100, E110, E111 are derivedaccording to the above formulae. The marked orientation dependence ofthe temperature curve is obvious from this figure. The question can nowbe posed for what direction, that is to say what value of 1 thebehaviour required of the material in accordance with the invention willbe available and g and e are approximately equal to zero. With the abovementioned formulae and with the temperature coefficient of a singlecrystal obtained from the curves it is found that of 300 K.

g=0 at $20.09 and e=0 at @2032.

g is negative for i 0.09 and e is negative for I 0.32. It appears to bequite certain therefore that, as regards the technical utilisation ofthe materials in accordance with the invention, this directiondependence is to be taken into account, and in fact for obtaininguniform results a definite texture, that is to say a more or lessrigidly determined value of I is to be imposed upon the structuralelement of sensibly constant elasticity. A definite I is thereforenecessary and is also a means in accordance with the invention foradjusting the temperature coefilcients of the elastic moduli. Anisotropic polycrystalline structure (whose I would be 0.2) canfrequently not be obtained through processing and it is a betterprocedure to produce a texture with suitable processing steps; accordingto this invention, this texture is then to orient with regard to theappearing stress in the structural element, e.g. the texture is producedwith regard to the given type and direction of stress or the structuralelement is cut in suitable orientation from the textured material. Thedecisive quantity for the texture relationship is in any case thequantity I taken as the mean over the polycrystalline material; P can berepresented in a so-called pole figure,

which is done in FIG. 3 (for the cubic case). The product-sum I musthave a value u2 for the elastic modulus and 02 for the shear modulus incubic materials. Similar relations as above hold for the temperaturecoefiicients of hexagonal materials when expressed in terms of singlecrystal-properties (however more complicated) in this case however IO.25 for the elastic modulus and I 0.25 for the shear modulus. Suchtexture relationships can be determined and controlled by wellknowntechniques of X-ray crystallography.

A texture can be achieved by drawing and/or rolling at room or elevatedtemperatures; recristallization annealing is also a process to create orsharpen a texture. In this connection, the conditions are frequentlysuch that, for example, in cubic body-centered materials (pure metals,alloys behave frequently otherwise) the 110 direction lies parallel tothe drawing or rolling direction I against this working direction), andfor cubic facecentered materials a portion of the crystallites adjustsits 100 direction and another part its 111 direction parallel to thedrawing or rolling direction (against the working direction, 1 has thenvalues between near 0 and 0.33).

In FIG. 4 there are set out the crystal structures of the elements andthe approximate phase structure of the binary alloy series of thetransition metals. The comparison with FIG. 1 now shows the previouslystated fact that the materials in accordance with the invention are notrestricted to a fixed crystal structure. On the contrary such materialsin accordance with the invention are consistent also with complexstructures if the condition is fulfilled that I\ (E is large and thatTABLE 1 40 atom percent Ir 60 atom percent- Nb 67 atom percent. Re 33atom percent. W 67 atom percent- R11 33 atom percent Ca 1-phaso. }Ofstructural type wMn. }Of structural type 015 (Laves phase).

According to this invention, given ranges of the electron concentratione/a (which are in fact a consequence of physical requirements concerningthe susceptibility) and processing steps which must impose minimumrespectively maximum values of (which is a description of the texture)are necessary to obtain structural materials whose rigidity isessentially temperature-independent. Useful materials have furthermoreto satisfy the conditions of high strength and hardness and smallmechanical losses (for example in oscillators for time-keeping devicesand electromechanical filters) and hardening processes are adopted suchas cold Working, dispersion hardening, precipitation hardening,polyphase structure, addition of alloying elements for chemicalhardening, phase transformation, either individually or combined witheach other.

Cooperative processes of the electrons characterise magnetic phenomena.On account of this cooperative aspect and therefore of the wide range ofinteraction, magnetic phenomena suffer strong perturbation by cold workor external fields; the classical ferromagnetic alloys with constantelastic modulus show in fact a marked decrease of the temperaturecoeificient when cold worked or exposed to a magnetic field. Suchinfluences are absent in materials according to the invention. A highdensity of states fi(E signifies in fact that geometrical and chemicalperturbations of the perfectly regular lattice, e.g. lattice faults andinterstitial impurity atoms, are well screened off (substitutionalatoms, either impurities or alloying additions are considered as bondingcomponents), while at the same time the reciprocal forces between thefaults diminish. The work-hardening of such materials is influenced andrelaxation processes which are connected with the interaction betweenstructural faults and impurities, may become important. In this respectthe very important property for the structural materials according tothe invention appears to be the fact that the elastic behaviour and itstemperature coefficient are modified not at all or only slightly by coldworking; this is in contrast to the classical ferromagnetic materials.Therefore this behaviour permits making full use of cold working stepsfor the production of a texture. It is however important in the case ofthe materials in accordance to this invention to supervise and controlthe content of dissolved substances of low atomic number, which aresusceptible to occupy interstitial places; in higher concentrationsthese substances may embrittle the materials and a lower content mayprovide relaxation processes. These relaxations modify the elasticitybehaviour over limited temperature ranges, and can be unwanted undercertain circumstances but wanted for the benefit of adapting anelasticity-temperature curve in others.

Alloy systems of structural materials according to this inventions, andwhich shall be capable of polyphase hardening, precipitation hardeningor dispersion hardening, have an electron concentration e/a where atleast the main phase lies in the previously given ranges. Thesehardening mechanisms involve different phases or a phase decomposition.The properties of the whole depend then on the proportions of presentphases, which themselves have different e/a-values and hence alsodifferent thermoelastic properties. Resulting from the inconsistency,there now appears a basically different behaviour of paramagneticalloys. As is evident from FIG. 1c, very small temperature coefficientsalternate with strongly negative coefficients of temperature within veryclosely adjacent e/a ranges. Definite relationships between thesetemperature coeificients now hold so that, for a given alloy which isbrought into the oversaturated metastable condition, the temperaturecoefficient is adjustable through a different annealing heat treatment.An example of this is the hardenable alloy system 25% zirconium and 75%niobium, which when rapidly cooled down from, for example, 1000 C., canthen be cold formed about by drawing (whereby a 110 drawn textureresults), whereafter a heat treatment at SSW-600 for four hours bringsthe required properties. Before this thermal treatment the temperaturecoefficient is positive, but with the phase separation, the zirconiumrich mixed crystal separates which has a markedly negative temperaturecoefficient, separates out and makes the temperature coetficient of thewhole more negative and towards zero. The electron concentration e/ a ofthis alloy amounts to 4.75.

Processes essentially similar take place in precipitation hardening. Amaterial in accordance with the invention of given electronconcentration is heat treated above the temperature dependent solubilitylimit (Solvus) and quenched, and then (possibly after cold forming) heattreated below the solubility limit. Due to the displacement of e/a inthe matrix and the contribution of the precipitate, the adjustment ofthe temperature coefiicient is achieved. Addition elements whereby theprecipitation hardening can be achieved without an excessive degree ofsolubility usually follow definite laws, known as the Hume-Rothery Laws.An example is an alloy of Nb and 5% Cr which has an e/a value of 5.1 andwhich can be subjected to a similar treatment to that above describedfor the Nb Zr alloy. In this case the precipitated phase effecting thehardening is NbCr Such alloys are suitable for use in tuned measuringdevices, for example clocks and in fact for its elastic elements in theform of spiral springs, tuning forks or other forms of vibratoryelement. Furthermore electromechanical filters may be made from suchalloys. Spring elements which have such small thermoelastic coefficientsare employed also for force measurement, for example in balances,electrical measuring instruments, levelling apparatus and similardevices. Another application of such alloys is for structural materialscapable of retaining their rigidity over a wide temperature range; suchneeds are for example present in turbines, planes, or rockets wherecomponents are subjected to mechanical stresses and whose elasticityshall not vary with temperature or where stresses might induceoscillations which should be controllable over a wide temperature range.

What we claims is:

1. A method of producing an elastically stressed body of a non-magneticelinvar which comprises:

(a) mixing in the liquid state metallic components so as to obtain analloy system whose atomic paramagnetic susceptibility x is larger than5010* e.m.u./ mol at room temperature and which has a negativetemperature coefficient of susceptibility d /dT,

(b) solidifying said metallic components,

(c) producing a preferred orientation of the crystallites of the systemby at least a mechanical treatment, followed by at least one additionalmechanical and/or thermal treatment, said preferred orientation beingdefined by the mean value of the product sum of the direction cosinetaken overall the crystallite orientations with respect to the stressdirection, said value being in cubic crystal structures greater than 0.2for the elastic modulus and smaller than 0.2 for the shear modulus, andsaid value being in hexagonal crystal structures smaller than 0.25 forthe elastic modulus and greater than 0.25 for the shear modulus.

2. A method as claimed in claim 1, wherein the alloy system has anelectron concentration e/a within the range of 2.73.5.

3. A method as claimed in claim 1, wherein the alloy system has anelectron concentration e/ a within the range of 4.45.3.

4. A method as claimed in claim 1, wherein the alloy system has anelectron concentration e/a within the range of 6.2-7.4.

5. A method as claimed in claim 1, wherein the alloy system has anelectron concentration e/ a within the range of 95-103.

6. A' method as claimed in claim 1, wherein the alloy system contains upto 10% by weight of a component promoting precipitation hardening.

7. A method as claimed in claim 1, wherein the alloy system contains upto 2% by Weight of a component promoting dispersion hardening.

8. A method as claimed in claim 1, wherein the elinvar is multiphase.

9. A method as claimed in claim 1, including the step of producing apreferred orientation by drawing.

10. A method as claimed in claim 1, including the step of producing apreferred orientation by rolling.

11. A method as claimed in claim 1, including the step of producing apreferred orientaiton by recrystallization annealing.

12. A method as claimed in claim 1, including the step of producing apreferred orientation by drawing or rolling, and recrystallizationannealing in the temperature region of homogeneous equilibrium phasestructure.

13. A method as claimed in claim 1, including the step of producing apreferred orientation by hot drawing.

14. A method as claimed in claim 1, including the step of producing apreferred orientation by hot rolling.

15. A method as claimed in claim 1, further comprising the steps of coldworking and annealing for obtaining an adjutment of the temperaturecoefficient.

16. A method as claimed in claim 1, further comprising the steps ofquenching and annealing at lower temperature for obtaining an adjustmentof the temperature coefficient.

17. A method as claimed in claim 1, wherein the temperaure coefficientis adjusted, sai-d adjustment including steps of a heat treatment abovethe equilibrium decomposition temperature and quenching, followed by aheat treatment below the decomposition temperature.

18. A method as claimed in claim 1, wherein an alloy system consistingof 10-40% zirconium and the remainder of niobium is rapidly cooled froma high temperaure, subjected to more than 30% of cold working and thensubjected to a heat treatment at 500-650 C. for a sumcient time toobtain the required temperature coefficient in the body when cooled.

19. A method as claimed in claim 6, wherein the precipitation hardeningcomponent consists of 2-10% chromium and the remainder niobium.

20. A method as claimed in claim 1, wherein the system contains oxygen,nitrogen, boron, beryllium or hydrogen in trace amounts.

References Cited UNITED STATES PATENTS 3,167,692 1/ 1965 Matthias -174X3,215,569 11/1965 Kneip, Jr. et al 75-174X 3,253,191 5/1966 Treuting eta1. 14811.5X 3,271,200 9/1966 Zwicker 14811.5 3,275,480 9/1966Betterton, Jr. et a1. 14811.5X 3,374,123 3/1968 Masumoto et al.148--11.5

L. DEWAYNE RUTLEDGE, Primary Examiner G. K. WHITE, Assistant ExaminerUS. Cl. X.R. 148--12.7, 13, 158

